1. Field of the Invention
The present invention relates to a composite hard magnetic material provided with excellent magnetization and temperature characteristics as well as good magnetic characteristics, and a method for producing the same.
2. Description of the Related Art
While a Smxe2x80x94Co system sintered magnet, Fexe2x80x94Ndxe2x80x94B system sintered magnet and Fexe2x80x94Ndxe2x80x94B system sintered magnet have been known in the art as magnetic materials having good performance superior to ferrite magnets, many researches are now under way aiming at novel alloy magnets such as a Fexe2x80x94Smxe2x80x94N system magnet having improved performance.
However, these magnetic materials require 10 atomic percentage (referred to at % hereinafter) or more of Nd or 8 at % or more of Sm to be contained, rendering a higher production cost than ferrite magnets owing to their higher content of expensive rare earth elements.
Although the ferrite magnets is more cheaply produced than these rare earth magnets, magnetic characteristics of the former have not been satisfactory, facilitating a demand for developing inexpensive magnetic materials that exhibit superior hard magnetism to the ferrite magnets.
For solving the problems as described above, the inventors of the present invention have invented hard magnetic materials (nano-composite Fexe2x80x94Mxe2x80x94B system magnets), as disclosed in Japanese Unexamined Patent Publication No.9-143641, that can be produced with low cost and have excellent hard magnetic characteristics containing one or more of elements among Fe, Co and Ni as main component as well as elements R comprising one or a plurality of rare earth elements, elements M comprising one or a plurality of Zr, Nb, Ta and Hf, and boron B, wherein 50% or more, preferably 60% or more, of the texture is composed of a fine crystalline phase with a mean crystal grain size of 100 nm or less with a balance of amorphous phases, the fine crystalline being mainly composed of bcc-Fe, Fexe2x80x94B compounds including solid solution elements and/or Fe14R2B1 (R represents one or more elements among rare earth elements).
The inventors of the present invention have also invented hard magnetic materials (nano-composite Smxe2x80x94Co system magnets), as hard magnetic materials provided with excellent hard magnetic characteristics disclosed in Japanese Examined Patent Publication No. 9-332134, having an amorphous phase and a fine crystalline phase containing Co as a main component as well as at least one or a plurality of elements Q among P, C, Si and B; Sm; one or a plurality of elements M among Nb, Zr, Ta and Hf; one or a plurality of elements R among Sc, Y, La, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and one or a plurality of elements X among Al, Ge, Ga, Cu, Ag, Pt and Au.
The nano-composite Fexe2x80x94Mxe2x80x94B system magnet as described above is an inexpensive magnet that have large remanent magnetization (Ir) and good magnetization characteristics besides having superior corrosion resistance to conventional Ndxe2x80x94Fexe2x80x94B magnets. However, the magnet has so small coercive force (iHc) of about 2 to 5 kOe that permeance coefficient is largely decreased when coercive force is decreased at high temperature. Accordingly, when the magnet is used for a constituting material of a sensor such as a throttle position sensor (an angle sensor) that is usually used at high a temperature, the sensor output tends to drift because magnetization is varied due to temperature changes.
While the coercive force (iHc) is large, temperature change of magnetization characteristics is small and corrosion resistance is good in the nano-composite Smxe2x80x94Co magnets, their remnant magnetization (Ir) as well as remanence ratio are so unsatisfactory that they can not be used for the constituting materials of the foregoing sensor that requires high magnetization characteristics, along with being high cost owing to their high content of expensive rare earth elements as in the Fexe2x80x94Ndxe2x80x94B system sintered magnets.
Accordingly, the object of the present invention for solving the problems as hitherto described is to provide a hard magnetic material that contains relatively a small amount of expensive rare earth elements and has excellent magnetization and temperature characteristics as well as good hard magnetic characteristics, and a method for producing the same.
For the purpose of providing a hard magnetic material containing relatively a small amount of expensive rare earth elements and has excellent magnetization and temperature characteristics as well as good hard magnetic characteristics and a method for producing the same, the nano-composite Fexe2x80x94Mxe2x80x94B system magnets and nano-composite Smxe2x80x94Co system magnets are especially noticed. It have been therefore presumed through collective studies and considerations that the foregoing problems would be solved by producing the hard magnetic materials using both of nano-composite Fexe2x80x94Mxe2x80x94B system hard magnetic powders and nano-composite Smxe2x80x94Co system hard magnetic powders.
Usually, when a hard magnetic material is produced by mixing two kinds of hard magnetic powders having different compositions with each other, steps representing the characteristics of the two kinds of hard magnetic powders are thought to be formed in the B-H loop of this hard magnetic material. Accordingly, a B-H loop without any steps can not be obtained when a hard magnetic material is produced using two kinds of the hard magnetic powders having different compositions with each other, rendering a difficulty in obtaining a hard magnetic material having an averaged characteristics between one hard magnetic powder and the other hard magnetic powder. Therefore, no production methods of the hard magnetic material using both of the nano-composite Fexe2x80x94Mxe2x80x94B system and nano-composite Smxe2x80x94Co system hard magnetic powders have not yet been established, thereby the foregoing assumption have never been proved nor applied for practical uses.
It was made clear, through further studies and considerations for completing the present invention, that a composite hard magnetic material, containing relatively a small amount of expensive rare earth elements and have excellent magnetization and temperature characteristics along with being provided with good hard magnetic characteristics without any steps in the B-H loop could be obtained by mixing, followed by consolidating, an alloy powder comprising an amorphous phase as a principal phase and containing at least Co and Sm, and an alloy powder comprising an amorphous phase as a principal phase and containing at least Fe and/or Co, rare earth elements R and B.
Accordingly, the object of the present invention is to provide a composite hard magnetic material, wherein a composite powder prepared by mixing an alloy powder comprising an amorphous phase as a principal phase and containing at least Co and Sm, and an alloy powder comprising an amorphous phase as a principal phase and containing at least Fe and/or Co, rare earth elements R and B are mixed and consolidated.
Preferably, the composite powder is consolidated by taking advantage of a phenomenon occurred when the phase in the alloy powder comprising an amorphous phase as a principal phase is crystallized.
In the composite hard magnetic material according to the present invention, a hard magnetic powder containing a main component Co and at least Sm and comprising a fine crystalline phase as a principal phase with a mean crystal grain size of 100 nm or less, and a hard magnetic powder containing at least Fe and/or Co, rare earth elements R, and B and comprising a fine crystalline phase as a principal phase with a mean crystal grain size of 100 nm or less are mixed and consolidated.
It is preferable that the composite hard magnetic material according to the present invention has a remnant magnetization (Ir) of 0.6T or more, the ratio between saturation magnetization (Is) and remnant magnetization (Ir) of 0.6T or more and coercive force (iHc) of 2 to 9 kOe.
According to the composite hard magnetic material of the present invention as hitherto described, the alloy powder comprising an amorphous phase as a principal phase and containing at least Co and Sm, or the hard magnetic powder containing a main component Co and at least Sm and comprising a fine crystalline phase as a principal phase with a mean crystal grain size of 100 or less is represented by the following composition formula:
(Co1xe2x88x92fTf)100xe2x88x92xxe2x88x92yxe2x88x92zxe2x88x92tMxSmyRzQt
wherein T denotes one or two elements of Fe and Ni; M denotes one or a plurality of elements among Nb, Zr, Ta and Hf; R denotes one or a plurality of elements among Sc, Y, La, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; and Q denotes one or a plurality of elements among P, C, Si and B; f being in the range of 0xe2x89xa6f less than 0.5, x being in the range of 0xe2x89xa6xxe2x89xa64, y being in the range of 8xe2x89xa6yxe2x89xa616, z being in the range of 0xe2x89xa6zxe2x89xa65, t being in the range of 0.5xe2x89xa6txe2x89xa610 and x+y+z being in the range of 8xe2x89xa6x+y+zxe2x89xa616 in at %, respectively.
According to the composite hard magnetic material of the present invention as hitherto described, the alloy powder comprising an amorphous phase as a principal phase and containing at least Co and Sm, or the hard magnetic powder containing a main component Co and at least Sm and comprising a fine crystalline phase as a principal phase with a mean crystal grain size of 100 or less is represented by the following composition formula:
(Co1xe2x88x92fTf)100xe2x88x92xxe2x88x92yxe2x88x92zxe2x88x92txe2x88x92uMxSmyRzQtXu
wherein T denotes one or two elements of Fe and Ni; M denotes one or a plurality of elements among Nb, Zr, Ta and Hf; R denotes one or a plurality of elements among Sc, Y, La, Ce, Pr, Nd, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu; Q denotes one or a plurality of elements among P, C, Si and B; and X denotes one or a plurality of elements among Al, Ge, Ga, Ag, Pt and Au; f being in the range of 0xe2x89xa6f less than 0.5, x being in the range of 0xe2x89xa6xxe2x89xa64, y being in the range of 8xe2x89xa6yxe2x89xa616, z being in the range of 0xe2x89xa6zxe2x89xa65, t being in the range of 0.5xe2x89xa6txe2x89xa610, u being in the range of 0xe2x89xa6uxe2x89xa65 and x+y+z being in the range of 8xe2x89xa6x+y+zxe2x89xa616 in at %, respectively.
In the composite hard magnetic material according to the present invention as hitherto described, f representing the composition ratio of the powder above is in the range of 0.2xe2x89xa6f less than 0.5 in at %.
Also, the composite hard magnetic material as hitherto described essentially contains Nb.
The composite hard magnetic material as hitherto described at least contains an alloy powder comprising an amorphous phase a principal phase and containing at least Fe and/or Co, rare earth elements R, and B, or Fe and/or Co, rare earth elements R and B;
the hard magnetic powder having a fine crystalline phase as a principal phase with a mean particle size of 100 nm or less being represented by the following composition formula:
TgMhRjBk
wherein T represents one or more elements essentially consisting of Fe or Co among Fe, Co and Ni; M represents one or more elements among Zr, Nb, Ta, Hf, Ti, V, Mo and W; R represents one or more elements among rare earth elements; and B represents boron; g, h, j and k indicating composition ratios are in the range of 50xe2x89xa6g, 0xe2x89xa6hxe2x89xa615, 3xe2x89xa6jxe2x89xa620 and 2xe2x89xa6kxe2x89xa620 in at %, respectively.
Also, g, h, j and k indicating the composition ratios in the composition formula of the powder above are in the range of 80xe2x89xa6gxe2x89xa693, 0.5xe2x89xa6hxe2x89xa65, 3xe2x89xa6jxe2x89xa610 and 3xe2x89xa6kxe2x89xa67 in the composite hard magnetic material as hitherto described.
Further, g, h, j and k indicating the composition ratios in the composition formula of the powder above are in the range of 86xe2x89xa6gxe2x89xa693, 0.5 less than hxe2x89xa63, 3xe2x89xa6jxe2x89xa67 and 3xe2x89xa6kxe2x89xa65 in the composite hard magnetic material as hitherto described.
The composite hard magnetic material as hitherto described at least contains an alloy powder comprising an amorphous phase as a principal phase and containing at least Fe and/or Co, rare earth elements R, and B, or Fe and/or Co, rare earth elements R and B;
the hard magnetic powder having a fine crystalline phase as a principal phase with a mean particle size of 100 nm or less being represented by the following composition formula:
TgMhRjBkEm
wherein T represents one or more elements essentially consisting of Fe or Co among Fe, Co and NI; M represents one or more elements among Zr, Nb, Ta, Hf, Ti, V, Mo and W; R represents one or more elements among rare earth elements; B represents boron; and E represents one or more elements among Cr, Al, Pt, Ru, Rh, Pd, Os, Ir, Cu, Ag, Au, Sc, Zn, Sn, Re and Mn; g, h, j, k and m indicating composition ratios are in the range of 50xe2x89xa6g, 0xe2x89xa6hxe2x89xa615, 3xe2x89xa6jxe2x89xa620, 2xe2x89xa6kxe2x89xa620 and 0xe2x89xa6mxe2x89xa610 in at %, respectively.
Also, g, h, j, k and m indicating composition ratios in the composition formula of the powder above are in the range of 80xe2x89xa6gxe2x89xa693, 0.5xe2x89xa6hxe2x89xa65, 3xe2x89xa6jxe2x89xa610, 3xe2x89xa6kxe2x89xa67 and mxe2x89xa65 in at %, respectively, in the composite hard magnetic material according to the present invention as hither to described.
Further, g, h, j, k and m indicating composition ratios in the composition formula of the powder above are in the range of 86xe2x89xa6gxe2x89xa693, 0.5xe2x89xa6hxe2x89xa63, 3xe2x89xa6jxe2x89xa67, 3xe2x89xa6kxe2x89xa65 and 0.1xe2x89xa6mxe2x89xa65 in at %, respectively, in the composite hard magnetic material according to the present invention as hither to described.
The composite hard magnetic material according to the present invention as hitherto described at least contains an alloy powder comprising an amorphous phase as a principal phase and containing at least Fe and/or Co, rare earth elements R, and B, or Fe and/or Co, rare earth elements R and B;
the hard magnetic powder having a fine crystalline phase as a principal phase with a mean particle size of 100 nm or less being represented by the following composition formula:
TgMhRjBkGn
wherein T represents one or more elements essentially consisting of Fe or Co among Fe, Co and NI; M represents one or more elements among Zr, Nb, Ta, Hf, Ti, V, Mo and W; R represents one or more elements among rare earth elements; B represents boron; and G represents one or more elements among C, Ga, Ge, P, Sb, In, B and As; g, h, J, k and n indicating composition ratios are in the range of 50xe2x89xa6g, 0xe2x89xa6hxe2x89xa615, 3xe2x89xa6jxe2x89xa620, 2xe2x89xa6kxe2x89xa620 and 0xe2x89xa6nxe2x89xa610 in at %, respectively.
Also, g, h, j, k and n indicating composition ratios in the composition formula of the powder above are in the range of 80xe2x89xa6gxe2x89xa693, 0.5xe2x89xa6hxe2x89xa65, 3xe2x89xa6jxe2x89xa610, 3xe2x89xa6kxe2x89xa67 and nxe2x89xa65 in at %, respectively, in the composite hard magnetic material according to the present invention as hitherto described.
Further, g, h, j, k and n indicating composition ratios in the composition formula of the powder above are in the range of 86xe2x89xa6gxe2x89xa693, 0.5xe2x89xa6hxe2x89xa63, 3xe2x89xa6jxe2x89xa67, 3xe2x89xa6kxe2x89xa65 and 0.1xe2x89xa6nxe2x89xa65 in at %, respectively, in the composite hard magnetic material according to the present invention as hitherto described.
The composite hard magnetic material according to the present invention as hitherto described at least contains an alloy powder comprising an amorphous phase as a principal phase and containing at least Fe and/or Co, rare earth elements R, and B. or Fe and/or Co, rare earth elements R and B;
the hard magnetic powder having a fine crystalline phase as a principal phase with a mean particle size of 100 nm or less being represented by the following composition formula:
TgMhRjBkEmGn
wherein T represents one or more elements essentially consisting of Fe or Co among Fe, Co and NI; M represents one or more elements among Zr, Nb, Ta, Hf, Ti, V, Mo and W; R represents one or more elements among rare earth elements; B represents boron; E represents one or more elements among Cr, Al, Pt, Ru, Rh, Pd, Os, Ir, Cu, Ag, Au, Sc, Zn, Sn, Re and Mn and G represents one or more elements among C, Ga, Ge, P, Sb, In, B and As; g, h, j, k, m and n indicating composition ratios are in the range of 50xe2x89xa6g, 0xe2x89xa6hxe2x89xa615, 3xe2x89xa6jxe2x89xa620, 2xe2x89xa6kxe2x89xa620, 0xe2x89xa6mxe2x89xa610 and 0xe2x89xa6nxe2x89xa610 in at %, respectively.
Also, in the composite hard magnetic material according to the present invention as hitherto described, g, h, j, k, m and n indicating the composition ratios in the composition formula of the powder above are in the range of 80xe2x89xa6gxe2x89xa693, 0.5xe2x89xa6hxe2x89xa65, 3xe2x89xa6jxe2x89xa610, 3xe2x89xa6kxe2x89xa67, mxe2x89xa65 and nxe2x89xa65 in at %, respectively.
Further, g, h, j, k, m and n indicating the composition ratios in the composition formula of the powder above are in the range of 86xe2x89xa6gxe2x89xa693, 0.5xe2x89xa6hxe2x89xa63, 3xe2x89xa6jxe2x89xa67, 3xe2x89xa6kxe2x89xa65, 0.1xe2x89xa6mxe2x89xa65 and 0.1xe2x89xa6nxe2x89xa65 in at %, respectively in the composite hard magnetic material according to the present invention as hitherto described.
The composite hard magnetic material according to the present invention as hitherto described comprises a Fe phase of the bcc structure (body-centered cubic structure) or a FeCo phase of the bcc structure or a bcc phase containing both of these phases, a R2Fe14B phase (R represents one or more elements among rare earth elements), a SmCo phase and a balance of an amorphous phase, one or more of the crystalline phases among the crystalline phases comprising fine crystalline phases with a mean crystal grain size of 100 nm or less.
The composite hard magnetic material according to the present invention having any of the constructions as described above is preferably magnetized along the direction parallel to the pressure impressing direction when the composite powder is consolidated.
The composite hard magnetic material according to the present invention has a rate of temperature change of magnetization at a permeance coefficient of 1 to 10 of xe2x88x920.04%/xc2x0 C. or less in the temperature range from room temperature through 120xc2x0 C.
In the composite hard magnetic material according to the present invention having any of the construction as described above, the alloy powder comprising an amorphous phase as a principal phase and containing at least Co and Sm, and the alloy powder having an amorphous phase as a principal phase and containing at least Fe and/or Co, rare earth elements R and B are mixed in a proportion of 5:95 to 80:20 in the composite powder.
In the composite hard magnetic material according to the present invention having any of the construction as described above, the alloy powder comprising an amorphous phase as a principal phase and containing at least Co and Sm, and the alloy powder comprising an amorphous phase as a principal phase and containing at least Fe and/or Co, rare earth elements R and B, are preferably mixed in a proportion of 1:1 in the composite powder.
In the steps comprising; mixing an alloy powder comprising an amorphous phase as a principal phase and containing a main component Co and at least Sm, and an alloy powder comprising an amorphous phase as a principal phase and containing at least Fe and/or Co, rare earth elements R and B; and consolidating the composite powder, the composite powder is consolidated by taking advantage of a softening phenomenon occurred by crystallization of the amorphous phase in the alloy powder comprising an amorphous phase as a principal phase.
In the method for producing a composite hard magnetic material according to the present invention as hitherto described, the composite hard magnetic material is magnetized along the direction parallel to the pressure impressing direction during or after consolidating the composite powder.
In the method for producing a composite hard magnetic material according to the present invention, a hard magnetic powder containing a main component Co and at least Sm and comprising a fine crystalline phase as a principal phase with a mean crystal grain size of 100 nm or less, a hard magnetic powder containing at least Fe and/or Co, rare earth elements R and B and comprising a fine crystalline phase as a principal phase with a mean crystal grain size of 100 nm or less, and a resin are mixed and consolidated.
It is preferable in the method for producing the composite hard magnetic material according to the present invention as hitherto described that the composite magnetic material is magnetized along the direction parallel to the pressure impressing direction during or after consolidating the composite powder.